1. Field of the Invention
The invention relates to processes for etching semiconductor fusions to change their electrical characteristics and more particularly to a process for etching fusions to reduce the firing current to a predetermined desired value.
2. Description of the Prior Art
It is well known in the prior art that the firing current of fusions used in thyristors can be reduced by etching the fusion to selectively remove semiconductor material which is exposed in an area adjacent the gate electrode. In the prior art this etching was performed using a small glass dropper to place an etching solution comprising hydrofluoric, nitric, and acetic acids on the area to be etched. Normally, this etching process is carried out prior to spin etching and passivation in order to avoid contamination of these coatings. However, the etching could be done after the passivation with a great deal of operation care and skill due to the possibility of damaging the passivation layer. The care and skill required made prior art etching procedure impractical. It is also known in the prior art that silicon can be plasma etched.